import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  double width = 0;
  double height = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          const Text(
            'You have pushed the button this many times:',
          ),
          Text(
            '$_counter',
            style: Theme
                .of(context)
                .textTheme
                .headline4,
          ),
          //没有给定大小时根据子控件大小自适应，如设置alignment，则根据alignment参数值确定(只适用于宽度)
          Container(
            margin: EdgeInsets.symmetric(horizontal: 16),
            padding: EdgeInsets.symmetric(horizontal: 16),
            height: 100,
            decoration: BoxDecoration(
                borderRadius: BorderRadius.circular(16),
                color: Colors.red,
                border: Border.all(width: 2, color: Colors.green)),
            width: double.infinity,
            child: const Text('textsdasdas d'),
          ),
          const SizedBox(
            height: 10
          ),
          Container(
            width: MediaQuery.of(context).size.width,
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: const <Widget>[
                Text('Hello World'),
                Text('Hello World'),
                Text('Hello World'),
                Text('Hello World'),
                Text('Hello World'),
              ],
            ),
          ),

          Row(
            children: const <Widget>[
               Text('textsdasdas d'),
               Text('textsdasdas d'),
               Text('textsdasdas d'),
               Text('textsdasdas d'),
            ],
          ),
          ListView.builder(
            itemBuilder: (context, index) {
              return const Text('textsdasdas d');
            },
            shrinkWrap: true,
            itemCount: 20,
          ),
          SizedBox(
            width: width,
            height: height,
            child: const Text(
                'textssadaslkdalksasdasdasdasd asdasldasdalskdjlkasjdlkajsldkjlaksjdlkasjdlkjaslkdjlkajsdlasjdlkjaslkjalskjdlkasjdlkdlkdasdas d'),
          )
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}
